Getting rid of AudioHardwareConfig and its synchronous IPC.

content/renderer/media/audio_renderer_sink_cache_impl.cc

Index: content/renderer/media/audio_renderer_sink_cache_impl.cc
diff --git a/content/renderer/media/audio_renderer_sink_cache_impl.cc b/content/renderer/media/audio_renderer_sink_cache_impl.cc
index 9fef7d0937b1dc594ee067d45f10a1ef6363b2ae..e571819fb6400c4ffcb2551461bb12ed163dd7a7 100644
--- a/content/renderer/media/audio_renderer_sink_cache_impl.cc
+++ b/content/renderer/media/audio_renderer_sink_cache_impl.cc
@@ -79,16 +79,27 @@ media::OutputDeviceInfo AudioRendererSinkCacheImpl::GetSinkInfo(
     // Ignore session id.
     base::AutoLock auto_lock(cache_lock_);
 
-    auto cache_iter =
-        FindCacheEntry_Locked(source_render_frame_id, device_id,
-                              security_origin, false /* unused_only */);
-
-    if (cache_iter != cache_.end()) {
-      // A matching cached sink is found.
-      DVLOG(1) << "GetSinkInfo: address: " << cache_iter->sink.get()
-               << " - reused a cached sink.";
-
-      return cache_iter->sink->GetOutputDeviceInfo();
+    if (media::AudioDeviceDescription::IsDefaultDevice(device_id)) {
+      if (default_device_info_)
+        return default_device_info_.value();
+
+      // Otherwise, there is no default device cached.
+      DCHECK(FindCacheEntry_Locked(source_render_frame_id, device_id,
+                                   security_origin,
+                                   false /* unused_only */) == cache_.end());

[Guido Urdaneta, 2016/07/05 15:10:39]

the /* unused_only */ comment does not add any information to me.

+    } else {
+      // Looking up a cached non-default device.
+      auto cache_iter =
+          FindCacheEntry_Locked(source_render_frame_id, device_id,
+                                security_origin, false /* unused_only */);
+
+      if (cache_iter != cache_.end()) {
+        // A matching cached sink is found.
+        DVLOG(1) << "GetSinkInfo: address: " << cache_iter->sink.get()
+                 << " - reused a cached sink.";
+
+        return cache_iter->sink->GetOutputDeviceInfo();
+      }
     }
 
     // No matching sink found, create a new one.
@@ -101,6 +112,10 @@ media::OutputDeviceInfo AudioRendererSinkCacheImpl::GetSinkInfo(
 
     // Cache a newly-created sink.
     cache_.push_back(cache_entry);
+
+    // Cache information for default output device.
+    if (media::AudioDeviceDescription::IsDefaultDevice(device_id))
+      default_device_info_ = cache_entry.sink->GetOutputDeviceInfo();
   }
 
   // Schedule it for deletion.
@@ -142,6 +157,10 @@ scoped_refptr<media::AudioRendererSink> AudioRendererSinkCacheImpl::GetSink(
 
   cache_.push_back(cache_entry);
 
+  // Update cached information for default output device.
+  if (media::AudioDeviceDescription::IsDefaultDevice(device_id))
+    default_device_info_ = cache_entry.sink->GetOutputDeviceInfo();
+
   DVLOG(1) << "GetSink: address: " << cache_entry.sink.get()
            << " - no unused cached sink found, created a new one."
            << " source_render_frame_id: " << source_render_frame_id